1 Mutual recognition of national measurement standards and of cal-ibration and measurement certificates issued by national metrol-ogy institutes The essential points The Mutual Recognition Arrangement (MRA) has been drawn up by t-he International Committee of weights and Measures (CIPM), underthe authority given to it in the Metre Convention, for signatureby directors of the national metrology institutes (NMIs) of Mem-ber States of the Convention. Objectives ．to establish the degree of equivalence of national measurementstandards maintained by NMIs; ．to provide for the mutual recognition of calibration and meas-urement certificates issued by NMIs; ．thereby to provide governments and other parties with a securetechnical foundation for wider agreements related to internat-ional trade, commerce and regulatory affairs. Process ．international comparsions of measurements, to be known as keycomparisions; ．supplementary international comparisions of measurements;．quality systems and demonstrations of competecnce by NMIs.Outcome ．statements of the measurement caopabilities of each NMI in adatabase maintained by the BIPM and publicly available on theWeb. Engagement NMI directors sign the MRA with the approval of the appropriateauthorities in their own country and thereby: ．aocept the process specified in the MRA for establishing thedatabase; ．recognize the results of key and supplementary comparisions asstated in the database; ．recognize the calibration and measurement capabilities of oth-er participating NMIs as stated in the database. Exclusions ．signature of the MRA engages NMIs but not necessarily any oth-er agency in their country; ．responsibility for the results of calibrations and measuremen-ts rests wholly with the NMI that makes them and is not, thro-ugh the MRA, extended to any other participating NMI. Organizational structure ．overall coordination is by the BIPM under the authority of theCIPM, which is itself under the authority of the Member Statesof the Metre Convention; ．the Consultative Committees of the CIPM, the Regional Metrolo-gy Organizations and the BIPM are responsible for carrying outthe key and supplementary comparisons; ．a Joint Committee of the Regional Metrology Organizations andthe BIPM is responsible for analysing and transmitting entriesinto the database for the calibration and measurement capabil-ities declared by the NMIs. Preamble National accreditation and regulatory bodies require multilater-al agreements or arrangements to define the conditions under wh-ich they can accept calibration, measurement and test certifica-tes issued by laboratories accredited in other countries. Theseagreements or arrangements depend for their validity on the ac-curacy of national mesurement standards and of calibration andmeasurement certificates issued by national metrology institut-es (NMIs). This arrangement provides for the mutual recognition of nationa-l mesaurement standards and of calibration and measurement cert-ificates issued by national metrology institutes, and is foundedon the efforts of each individual national metrology instituteto base its measurements and measurement uncertainties on SI un-its. To put the criteria for mutual recognition on an objective foot-hing, the arrangement calls upon: (a) the results of a set of k-ey comparisons carried out using specified procedures which leadto a quantitative measure of the dagree of equivalence of natio-nal measurement standards; (b) the operation by each NMI of a s-uitable way of assuring quality; and (c) successful participati-on by each NMI in appropriate supplementary comparisons. Togeth-er, these three procedures demonstrate to participating institu-tions the degree to which each may have confidence in the resul-ts reported by others, and so promote mutual confidence betweenthem. For the purposes of this arrangement, the degree of equivalenceof measurement standards is taken to mean the degree to which t-hese standards are consistent with reference values determinedfrom the key comparisons and hence are consistent with one anot-her. Each reference value is referred to as a key comparison re-ference value and, in most cases, it can be considered to be aclose, but not necessarily the best, approximation to the SI va-lue. The degree of equivalence of a national measurement standa-rd is expressed quantitatively in terms of its deviation from t-he key comparison reference value and the uncertainty of this d-eviation. This arrangement is in two parts: through part one, signatoriesrecognize the degree of equivalence of national measurement sta-ndards of participating national metrology institutes; throughpart two, the signatories recognize the validity of calibrationand measurement certificates issued by participating institutes.Formally, this document is a technical arrangement among direct-ors of the national metrology institutes of Member States of theMetre Convention and it is not a diplomatic treaty. It is drawnup by the CIPM under the Metre Convention and it is neither anextension to the Convention nor a replacement of any Article ofthe convention. The directors who in due course decide to signthe arrangement do so with the approval of the appropriate gove-nmental or other offical authorities in their own country. It isexpected that participation in this arrangement will open the w-ay to, and provide the technical basis for, wider agreements re-lated to trade, commerce and regulatory affairs, signed by thecompetent authorities in each country or region. Participation in the arrangement through their regional metrolo-gy organization is also open to the NMIs of States and Economiesthat are Associates of the CGPM. 1 The arrangement 1.1 This is an arrangement between national metrology instituteswhich specifies terms for the mutual recognition of nationalmeasurement standards and for recognition of the validity ofcalibration and measurement certificates issued by nationalmetrology imstitutes. It is drawn up by the CIPM with the a-uthority given it under Article 10 (1921) of the Rules Anne-xed to the Metre Convention. 1.2 this arrangement is in two parts as specified in paragraph 2below:part one concerns national measurement standards andpart two concerns calibration and measurement certificates.1.3 Participation national metrology institutes, signatories tothis arrangement, may choose to limit their participation topart one, the recognition of national measurement standards.1.4 each signatory to this arrangement is the national metrologyinstitute designated by the appropriate national government-al or other offical authority of the Member State of the Me-tre Convention as being responsible for national measurementstandards. For any state that has more than one such design-ated institute, the arrangement is signed by one instituteon behalf of all, the names of the other institutes being a-ttached to the document. 1.5 Designated NMIs of States or Economies that are Associatesof the CGPM may participate in the arrangement only throughtheir regional metrology organizations by signing a declara-tion, appended to this arrangement. 1.6 Intergovernmental and international organizations designatedby the CIPM may also participate in the arrangement. 2 Scope of the arrangement 2.1 participating national metrology institutes, listed in Appe-ndix A, recognize the degree of equivalence of national mea-surement standards, dervied from the results of key compari-sons, for the quantities and values specified in Appendix B.This constitutes part one of the arrangement. 2.2 Participating institutes recognize the validity of calibrat-ion and measurement certificates issued by other participat-ing institutes for the quantities and ranges specified in A-ppendix C.This constitutes part two of the arrangement. 3 Technical basis of the arrangement 3.1 The technical basis of this arrangement is the set of resul-ts obtained in the course of time through key comparisons c-arried out by the Consultative Committees of the CIPM, theBIPM and the regional metrology organizations (RMOs), and p-ublished by the BIPM and maintained in the key comparison d-atabase. Detailed technical provisions are given in the Tec-hnical Supplement to this arrangement. 3.2 Key comparisons carried out by Consultative committees or t-he BIPM are referred to as CIPM key comparisons; key compar-isons carried out by regional metrology organizations are r-eferred to as RMO key comparisons; RMO key comparisons mustbe linked to the corresponding CIPM key comparisons by meansof joint participants. The degree of equivalence derived fr-om an RMO key comparison has the same status as that derivedfrom a CIPM key comparison. 3.3 A Joint Committee of the RMOs and the BIPM (the Joint commi-ttee or JCRB), created by the CIPM, is responsible for thecoordination of data provided by the RMOs, and other actionsundertaken by them to promote confidence in calibration andmeasurement certificates (see paragraph 9.3). 4 Responsibilities of the Consultative Committees of the CIPMThe Consultative Committees have the responsibility for choos-ing the key comparisons listed in Appendix D and affirming thevalidity of the results. The particular responsibilities of t-he Cosultative Committees are detailed in the Technical Suppl-ement. 5 Responsibilities of the regional metrology organizationsThe national metrology institutes that are signatories to thisarrangement undertake to put in place appropriate strutures w-ithin their RMOs so that the RMOs may: a) make proposals to the Consultative Committees on the choiceof key comparisons; b) carry out the RMO key comparisons, described in the Techni-cal Supplement, corresponding to the CIPM key comparisons;c) participate in the JCRB (see paragraphs 9.3 and 9.4 below);d) carry out supplementary comparisons and other actions desi-gned to support mutual confidence in the validity of calib-ration and measurement certificates issued by participatinginstitutes (see paragrph 7.3 below). 6 Participation in key and supplementary comparisons 6.1 Participation in a CIPM key comparison is open to laborator-ies having the highest technical competence and experience,normally the member laboratories of the appropriate Consult-ative Committee. Those laboratories that are not members ofa consultative committee and not NMIs must be nominated bythe designated national metrology institute referred to inparagraph 1.4 as being responsible for the relevant nationalmeasurement standards. In choosing participants, the Consul-tative Committees should take proper account of regional re-presentation. The number of laboratories participating in CIPM key comparisons may be restricted for technical reasons.6.2 Participation in key comparisons organized by an RMo is opento all RMO members and to other institutes that meet the ru-les of the regional organization (including institutes invi-ted from outside the region) and that have technical compet-ence appropriate to the particular comparsion. 6.3 Participation in RMO supplementary comparisons is open to t-hose institutes meeting the requirements specified in pargr-aph 6.2. 7 Confidence in measurements 7.1 Confidence in measurements is an essential prerequiste tointernational trade and facilitates almost every task in theindustrialized world. To a large extent this confidence alr-eady exists and is based on the SI, which is the cornerst o-ne of the international measurement system, as realizsed bythe national metrology institutes. The function of this mut-ual recognition arrangement is to extend and consolidate pre-existing worldwide confidence in measurements. 7.2 Institutes participating in this arrangement are expected toextend existing international confidence in teir activitiesby publishing regular reports on the work of their laborato-ries and transmitting them to the BIPM, by participation inrelevant conferences, and by taking part in the activitiesorganized by the BIPM. 7.3 In addition to participation in the key and supplementary c-omparisons, identified in paragraph 6, recognition of calib-ration and measurement certificates requires one of the fol-lowing procedures in order to establish the necessary mutualconfidence: a) an NMI that chooses for its calibration and measurementservices a quality system that meets the requirements of ISO Guide 25 or equivalent for an NMI, assessd by an acc- reditation body fulfilling the requirements of ISO Guide 58, declares its calibration measurement capabilities (s- ee paragraph T.7) and submits them to the local RMo for review and transmission to the Joint Committee for analy- sis and inclusion in Appendix C; b) an NMI that chooses to use a different way of assuring q-uality or chooses a different quality system, or ISO Gui- de 25 without third - party assessment, for its calibrat- ion and measurement service declares its calibration mea- surement capabilities (see paragraph T.7) and submits th- em to the local RMO for review and transmission to the J- oint Committee for analysis and inclusion in Appendix C. Demonstration of competence and capability may reuqire visi-ts and examination of procedures by an NMI and/or by peersselected by the local RMO. 7.4 Nothing in this arrangement is intended to limit the freedomof one or more signatories to establish mutual recognition,as specified in paragraphs 2.1 and 2.2, outside this arrang-ement. 8 Disputes in the operation of the arrangement This arrangement is operated by the BIPM in close consultationwith the Consultative committees and the RMOs whose responsib-ility it is, under paragraphs 4 and 5 above, to carry out andevaluate the results of the key comparisons. Disagreements th-at arise in the operation of this arrangement are discussed f-irst within the appropriate Consultative Committee, the RMO orthe Joint Committee and if not resolved there, are referred toteh CIPM. 9 Coordination 9.1 Overall coordination of activities related to this arrangem-ent resides with the CIPM. 9.2 Coordination of the key comparisons is effected through con-sultations between the Consultative Committees and the RMO's. 9.3 Coordination of the supplementary comparisons and other act-ions related to confidence in calibration and measurement c-ertificates undertaken by the regional metrology organizati-ons is carried out by the JCRB. The JCRB is created by the CIPM comprising representatives of the RMOs and is chaired bythe Director of the BIPM, Its terms of reference are givenin Appendix E. 9.4 Under the overall responsbility of the CIPM, the Joint Comm-ittee is responsible for analysing and maintaining the cont-ent of Appendix C. 10 Responsibility and liability for measurements 10.1 It is recognized and accepted by each signatory that thisarrangement cregtes no rights, liabilities or obligations that will have binding effects in national or internationallaw. 10.2 It is recognized and accepted by each signatory that thisarrangement covers, in each country, only the signatory in-stitute and other institutes represented by it It dose notnecessarilyextend to other metrological or regulatory bodi-es in that country. 10.3 Rsponsbility for all measurements made under this arrangem-ent rests wholly with the institute making the measurement-s. No responsibility for declared uncertainties of statmen-ts of quality is assumed by the CIPM, the BIPM, the Consul-tative Committees or the RMOs. 11 Signing this mutual recognition arrangement and bringing itinto force 11.1 The procedure for implementing this arrangement is as foll-ows: ．at the meeting of directors of national metrology instit-utes held on 23-25 February 1998, the directors were inv- ited to initial a draft of this arrangement. ．at the meeting of directors of national metrology instit-utes to be held at the time of the 21st CGPm in October 1 999, dircetors will be invited to sign this arrangment f- or an initial period of four years. New signatories may attach themselves to this arrangementatany time by application to the Director of the BIPM. 11.2 To withdraw from the arrangement, the Director of a signat-ory institute should notify the Director of the BIPM six m-onths prior to the effectivee date of withdrawal. The Dire-ctor of the BIPM will notifiy all other signatories of suchnotice of withdrawal not later than one month after it hasbeen received. 11.3 during the period from October 1999 until such time as thefirst round of key and supplementary comparisons has been completed and the quality systems specified in paragraph 7.3 put in place, the arrangement will operate in a transiti-onal mode. Provisional degrees of equivalence (Appendix B)will be based on the results of comparisons carried out si-nce about 1988, reviewed and approved by the Consultative committee for each filed and entered into the key comparis-on database referred to in paragraph 3.1. Provisional cali-bration Capabilities and measurement capbilities (Appendix-C) will be based on corresponding data reviewed by the RM-Os and analysed by the JCRB, taking into account the proc-edures specified in paragraph 7.3 and included in the key comparison database. 11.4 After the initial period of four years, signatiories may,with the approval of the appropriate govenmental or other official authorities in their own country, make changes tothis arrangement at meetings organized by the CIPM of dirc-etors of the national metrology institutes. 12 Status of national measurement standards calibrated by the B-IPM or by a national metrology institute Nothing in this arrangement restricts the rights under the M-etre Convention of participating national metrology institut-es to have their national standards calibrated by the BIPM orby another national metrology institute. The mutual recognit-ion of such standards depends upon subsequent participationin key or supplementary comparisons (see paragraphs 3 and 6above). 13 NMIs that are not members of an RMO Those NMIs that wish to participate in this arrangement buyare not members of an RMO, should either form a new RMO, orfor the purposes of this arrangement, associate themselves w-ith an existing RMO, whichever is the more appropriate. If n-either approach is possible, they should seek to make specialprovisions. 14 NMIs that are members of more than one RMO Those NMIs that are members of more than one RMO must declarewith which RMO they will paricipate in part two of this arra-ngement. 15 Entry of new RMOs into the joint Committee The entry of a new RMO into the Joint Committee is subject toapproval by the CIPM. The technical basis for this arrangement is the set of resul-ts obtained during the key comparisons carried out by the Co-nsultative Committees, the BIPM and the RMOs (paragraph 3.1). The following specify conventions and responsibilites rela-ting to the key comparisons. T.1 CIPM key comparisons lead to reference values, known askey comparison reference values. T.2 For the purposes of this arrangement, the term degree ofequivalence of measurement standards is taken to mean the degree to which a standard is consistent with the key co- mparison reference value. The degree of equivalence of e- ach national measurement standard is expressed quantitat- ively by two terms: its deviation from the key comparison reference value and the uncertainty of this deviation (at a 95% level of confidence). The degree of equivalence be- tween pairs of national measurement standards is express- ed by the difference of their deviations from the refere- nce value and the uncertainty of this difference (at a 95 % level of confidence). T.3 Although a key comparison reference value is normally aclose approximation to the corresponding SI value, it is possible that some of the values submitted by individual participants may be even closer. In a few instances, for example in some chemical measurements, there may be diff- iculty in relating results to the SI. Nevertheless, the key comparison reference value and deviations from it are good indicators of the SI value. For this reason, these values are used to express the degree of equivalence bet- ween the standards of paricipating laboratories. In some exceptional cases, a Consultative Committee may conclude that for technical reasons a reference value for a parti- cular key comparison is not appropriate; the results are then expressed directly in terms of the degrees of equiv- alence between pairs of standards. T.4 The results of the RMO key comparisons are linked to keycomparison reference values established by CIPM key comp- arisons by the common participation of some institutes in both CIPM and RMO comparisons. The uncertainty with which comparison data are propagated depends on the number of institutes taking part in both comparisons and on the qu- ality of the results reported by these institutes. T.5 The results of the CIPM and the RMO key comparisons, thekey comparison reference values, the deviations from the reference values and their uncertainties, together with other information necessary for their interpretation, are published by the BIPM and entered into the key comparison database. T.6 CIPM and RMO key comparisons must be carried out followi-ng the Guidelines for CIPM key comparisons published by the BIPM and available on the BIPM Web page. T.7 For calibration and measurement certificates, the quanti-ties, ranges and calibration and measurement capabilities expressed as an uncertainty (normally at a 95% level of confidence but in some cases it may be at a higher, spec- ified, level), are listed for each participating institu- te in Appendix C. They must be consistent with the resul- ts given in Appendix B, derived from the key comparisons. If, as a result of a key comparison, a significant unres- olved deviation from the key comparison reference value persists for the standard of a particular participating institute, the existence of this deviation is noted in A- ppendix C. In this case, the institute has the choice of either withdrawing from Appendix C one or more of the re- levant calibration and measurement services or increasing the corresponding uncertainties given in Appendix C. The calibration and measurement capabilities listed in Appen- dix C are analysed by the Joint Committee following the procedures given in 7.3 above. The calibration and measu- rement capabilities referred to in this paragraph are th- ose that are ordinarily available to the customers of an institute through its calibration and measurement servic- es; they are sometimes referred to as best measurement c- apabilities. T.8 Responsibilities of the Consultative Committees: the Con-sultative Committess have a prime role in choosing and i- mplementing key comparisons and in affirming the validity of the results. THeir particular responsibilities are: a) to identify the key comparisons in each field and mai- ntain a current list (Appendix D); b) to initiate and organize, with the collaboration of t- he BIPM, the execution of key comparisons at intervals to be decided individually for each comparison; c) to review the results of CIPM key comparisons and det- ermine the reference values and degrees of equivalence on the basis of the proposals of the appropriate work- ing groups; d) to approve the final report of CIPM key comparisons f- or publication by the BIPM; e) to examine and confirm the results of RMO key and sup- plementary comparisons and incorporate them in Append- ix B and key comparison database; f) to examine and confirm the results of bilateral key c- omparisons for entry into Appendix B and the key comp- arison database. T.9 RMO key comparisons: the RMO key comparisons extend themetrological equivalence established by the CIPM key com- parisons to a greater number of national metrology insti- tutes including those of States of Economies that are As- sociates of the CGPM. Redundancy, coherence and timeline- ss are important aspects of regional comparisons for they ensure that the overall system of comparisons is robust. Regional organizations therefore have a particular respo- nsibility for ensuring that: a) links with the CIPM key comparisons provide adequate redundancy through the participation of a sufficient number of laboratories in both sets of comparisons to ensure that links to the key comparison reference val- ues are established with acceptably low uncertainty; b) the procedures used in regional comparisons, and the evaluation of the results and uncertainties, are comp- atible with those used in the CIPM key comparisons; c) the timing of the RMO key comparisons is coordinated with, and is at least as frequent as, those of the CI- PM key comparisons; d) the results of RMO key comparisions are carefully eva- luated by the RMO, which also takes responsibility for ensuring that the proper procedures have been followed , and then the results are submitted for publication and to the relevant CC for incorporation in Appendix B and the key comparison database; e) the results of appropriately performed bilateral comp- arisons are considered and then submitted to the rele- vant Consultative Committee for incorporation in Appe- ndix B and the key comparison database; f) in the case that an RMO key comparison takes place be- fore the corresponding CIPM key comparison, the link to the subsequent key comparison reference value is d- eferred until both key comparisons are completed. T.10 supplementary comparisons : in addition to the key compa-risons, the Consultative Committees, the RMOs and the BI- PM may carry out supplementary comparisons to meet speci- fic needs not covered by key comparisons, including comp- arisons to support confidence in calibration and measure- ment certificates. The Joint Committee of the RMOs and the BIPM (see paragr- aph 9.3 above) provides a forum for the coordination, am- ong the regions, of the supplementary comparisons carried out by the RMOs in order to bolster confidence in calibr- ation and measurement certificates. Appendices to the arrangement Appendices A, B, C and D are maintained electronically in the k-ey comparison database held at the BIPM. During the initial fou-r-year period, the database (which was designed by the NIST) wi-ll be held jointly by the BIPM and the NIST. Appendix A List for national metrology institutes that are signatories tothe arrangement, together with their logos. Appendix B B1: Results of CIPM key comparisons. B2: Results of RMO key comparisons. B3: Results of supplementary comparisons. For each key comparison the following are included: ．individual values for each institute together with their decl-ared uncertainties; ．the key comparison reference value with its associated uncert-ainty; ．for each institute, the deviation from the key comparison ref-erence value and the uncertainty in that deviation (at a 95%level for confidence), i.e. its degree of equivalence; ．the degress of equivalence between the standards of each of t-he participating institutes. Appendix C Quantities for which calibration and measurement certificates a-re recognized by institutes participating in part two of the ag-reement. The qUantities, ranges and calibration and measurementcapabilities expressed as an uncertainty (normally at a 95% lev-el of confidence) are listed for each participating institute.Appendix D List of key comparisons. Appendix E Terms of reference of the Joint Committee of the Regional Metro-logy Organizations and the BIPM (JCRB). Glossary of terms used in this arrangement BIPM:Bureau International des Poids et Mesures. CGPM:General Conference of Weights and Measures. CIPM:International Committee of Weights and Measures. Calibration and measurement capability:the highest level of cal-ibration or measurement normally offered to clients, expressedin terms of a confidence level of 95%, sometimes referred to asbest measurement capability. Calibration or measurement certificate: a certificate issued bya national metrology institute and relating to a test, calibrat-ion or measurement of an instrument or a reference material (pe-rtaining either to physical or to chemical measurements). CIPM key comparison: a key comparison executed by a ConsultativeCommittee or the BIPM leading to a key comparison reference val-ue. Degree of equivalence of a measurement standard: the degree towhich the value fo a measurement standard is consistent with thekey comparison reference value. This is expressed quantitativelyby the deviation from the key comparison reference value and theuncertainty of this deviation. The degree of equivalence betweentwo measurement standards is expressed as the difference betweentheir respective deviations from the key comparison reference v-alue and the uncertainty of this difference. Key comparison: one of the set of comparisons selected by a Con-sultative Committee to test the principal techniques and methodsin the field (note that key comparisons may include comparisonsof representations of multiples and sub-multiples of SI base andderived units and comparisons of artefacts). Key comparison database: the database maintained by the BIPM wh-ich contains Appendices A, B, C and D of this Mutual RecognitionArrangement. Key comparison reference value: the reference value accompaniedby its uncertainty resulting from a CIPM key comparison. National metrology institute: the national metrology institutesignatory to this arrangement is the metrology institute design-ated by the appropriate national governmental or other officialauthority as that responsible for national measurement standard-s. RMO key comparison: a key comparison executed by an RMO. Note:only key comparisons carried out by a Consultative Committee orthe BIPM lead to a key comparison reference value. For a key co-mparison carried out by a regional metrology organization the l-ink to the key comparison reference value is obtained by refere-nce to the results from those institutes which have also takenpart in CiPM key comparison. Supplementary comparison: comparisons carried out by the Consul-tative Committees, the RMOs and the BIPM to meet specific needsnot covered by key comparisons, including comparisons to supportconfidence in calibration and measurement certificates. Appendix E Terms of reference of the joint Committee of the Regional Metro-logy Organizations (RMOs) and the BIPM. 1 The joint Committee is charged with a) Coordinating the activities among the RMOs in establishingconfidence for the recognition of calibration and measurem-ent cerificates, according to the terms of the Mutual Reco-gnition Arrangement (MRA); b) making policy suggestions to the RMOs and to the CIPM on t-he operation of the MRA; c) analysing the application by each RMO of the criteria of t-he MRA; d) analysing and entering into Appendix Cthe proposals of eachRMO in respect of the calibration and measurement capabili-ties of their member NMIs and reporting to the CIPM; e) facilitating appropriate inter-regional supplementary comp-arisons; f) writing an annual report on the activities of the Joint Co-mmittee to the CIPM and to the signatories of the MRA. 2 Membership and meetings of the joint Committee a) each RMO informs the Director of the BIPM of the name of i-ts official representative on the Joint Committee; b) at each meeting of the Joint Committee the representativesmay be accompanied by appropriate advisors; c) the Joint Committee operates by consensus; d) the Joint Committee should meet at least once a year.
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